Cascading shop compressors for better Altaros function

Well, the two CAT compressors are independent of each other, pumping into a common tank, backed by 10 gallons of air in each compressors tank. A check valve on each line is what makes them independent as it prevents air from one compressor filling the others tank.

As one compressor runs it’s pressure down, it’s motor starts up and recharges itself, the 2nd compressor does the same thing once it reaches the compressor start pressure. The CAT compressors cycle independently.

The booster is run by two pistons or stages, the booster pumps two pistons are powered by the shop compressors, they also provide air to be boosted. The Booster has a adjustable scba fill shut-off, mine is set at 4500 psi. Once that level is reached, the booster shuts off.

A fan setting directly on top of the roll cage cooks the shop compressors cylinders and insures a longer life to the pump/



Hope this makes it clearer.



Roachcreek

Eaglebeak, 



Thanks for the suggestions, it is always best to have options.
Seems like a lot of work and expense especially as it works fine now, however I have heard this from other members so I may change my mind later. I researched it quite a bit, and found using the check valves the best solution for me, not to mention it is done that way in a lot of industry settings. I have a gate valve coming so I can adjust the run times, but in my 71 year old damaged mind I want them coming on consecutive instead of at the same time to try for a steady or steadier air pressure. I did have them going on and off at the same time at first to check my electrical system. I decided against the larger oil filled compressors as I did not wish to have my house rewired. If I loose a compressor now my system will still run, albeit much slower, but if I loose a single large compressor it will take a month to a month and a half for an exchange, and compressors do fail. CAT is on the west coast, so that exchange would be just days. But the biggest thing is the oil smell that the oil filled compressors put out, I bought my house new, and plan on selling it after this Covid thing is solved to build on a lot in Asia near my wife’s family, it is my old folks home so to speak. When I sell, I want my home smelling like the clean desert air here and not like a Jiffylube. Now I understand not all large compressors are prone to this, but most are Chinese and I just don’t want to play in either of those lotteries


I am going to put all water filters on the low pressure side, and I plan on adding a dessitant type filter at the booster where the shop air enters. The booster as you know has both a oil/water filter and a dessitent filter. The water filled garbage cans are already there and just out of the picture 3 feet away, I bought and filled them on the day we went into quarantine last spring just in case the grid failed. With the cans there and filled, I plan on putting 20 feet of coiled hose into the water, and draining the water out of the hose like you suggest. We have very low humidity here in central Oregon, but never the less compressing air makes water. As a result it is a 20 minute $20.00 project and I like to experiment.

Only thing I plan on putting on the high side is a scba bottle when I fill it.

The biggest challenge so far has been getting compressors and tanks delivered undamaged, so far it is running 50/50, I have found although Walmart may not have the best price, they do pickup for free returns at my house, when you figure shipping in on a return to the east coast from the west coast, Walmart has by far the best deal.

Thanks again,

Roachcreek

I had to put the 2nd compressor on another line, they kept tripping the breaker using one outlet, and my furnace and aircon is on that line.

I ran a extension cord to a outlet in the kitchen to see how well the 2nd compressor ran, it did just fine.

When I started them up, they started and stopped at the same time, so I left them that way.

The run ratio for the compressor was 70-30 with the compressors running 30% of the time and off 70%. The system filled a 60 minute bottle from 4100 to 4500 in 40 minutes. Cylinder heads were 85-90 degrees, with one fan running on both. I have another fan coming and soon each compressor will have a cooling fan.

The garbage can with 280 lbs of water was a good workout for a skinny 71 year old, but as foretold here, not worth the effort, so I will get a couple desicantfilters instead.

Roachcreek

Henrik,



I ordered that filter yesterday, thanks for the tip.



Regards,

Roachcreek

CT’s,



Yes I had a lot of water and yes that hose gets hot.

I put12 inch fans on both of my CATS, it really helps with the heat. I do not get water in my Altaros oil/warter separator. But I do dry out my desiccant every use, and I have that desiccant filter shown by Henrik coming.

All this with humidity in the 20’s and low 30’s, to me it’s all about heat, the less you have, the less water and more longevity you get with your compressor.

With the 2nd compressor, cooled by fans, I do get less water in the three CAT 10 gallon tanks , mainly due to the improved on/off run ratio and rhe longer rest time the compressors get. I also only run during the morning hours when it is cooler and drain the tanks when done filling my scba tanks.

I contacted a CAT engineer about the heat when running one compressor, I was told that it would shorten the compressors life, when I informed him about the cooling fan and temps I was running at, he was impressed, he really liked that cooling fan Idea.

I would advise you to wait and see how this 2 compressor set up works for me before spending another 500 bucks on the plumbing, fans and 2nd CAT, however, so far it fills much faster, the CATS run less and cooler and I have less water coming out of my 3 my CATS tank. I still need to experiment with staggered start up and make sure the set up I have does not eat my CAT motors.


The CATS @ 90 psi put out 5.2 cfm, at 125 PSI it is probably @ 4 Cfm, so with two CATS , and bear in mind Hendricks compressor rating video’s and that I am guessing at this, I should be getting 8 cfm’s at the Altaros. All that leads to less heat and water.


I hope this helps,



Roachcreek

Here is some stats and observations from this mornings fill.

Room temp/humidity level 61 degrees/30 humidity.

700 psi fill on a 60 minute bottle. Time, 90 minutes.

Highest temperature on the braided hose temp, taken just as compressors shut off, 85F 

Highest head and cylinder sleeve temps as compressor shuts down, 85/115F

Compressor ratio for run time vrs off time, 30/70.

Water buildup in compressor tank, this is a subjective observation as I am eyeballing the spray on my cement garage floor, 1 table spoon compressor #1 vrs 1 teaspoon compressor #2.

The two CAT compressors seem to want to run at the same time and migrate to that cycle. The two fans cool down the compressor heads, sleeve and braided hose 10 to 20 degrees F between cycles.

About that air dryer, for the cost of that unit, you can purchase a 2nd CAT and fan and set it up and have enough money left over for an additional expired ebay scba tank. For me that works. With the 2nd compressor, fill rates are adequate, same as my Shoebox was, water buildup is minimal as the run temperature is much lower.

My Altaros desiccant filter did not change color in 90 minutes, when I get that larger desiccant filter from Alliexpress that Henrik was kind enough to provide, and plumb it into the line between the storage tank and Altaros booster, I think the two desiccant filters will remove any water from the Altaros to scba tank.. My Altaros water/oil separator is still dry.

One thing I have noticed is that when the scba tank pressure approaches 4100-4200 psi I detect a noise coming from the two pistons rhat resembles a sound like rubbing your hand on a balloon. I was tempted to put a drop of silicone oil into the shop air hose port on the Altaros, but decided to get Altaros advise first.

To recap, I used 2 CAT oilless compressors to avoid any oil smell, to avoid rewiring my garage for 220V and to assemble a setup that had 3 replaceable plug in components, the 2 CAT compressors and the Altaros booster. The 2 CATS are cheaper than the least expensive Chinese 220 volt junk compressor, and I wanted to avoid that Chinese junk connection as these forums have instilled in me a distrust of China compressors of any kind. I did have to run a 110 cord from my kitchen to my 2nd CAT, but that was far less expense than what a 22V rewire would cost as I had the cord.

So far, I am very happy with my set up.

‘Regards,

Roachcreek

One thing I should mention about why I choose not to wire my units together and ultimately choose to have then starting, running and stopping at the same time.

California AirTools makes two, models of 4 hp oilless compressors. Both models, whether 110 or 220v have the same two, 2hp hp motors with oilers pumps identical to mine, sitting on top of their respective air tanks. Both compressors motors and pumps come on at the same time and shutoff at the same time. There does not seem to be any special wiring for this.

Regards,


Roachcreek

Two were good, three works much better.

I have no idea how much a dive compressor costs, it is probably cheaper but way slower.

Initially I had just one CAT compressor, a couple of fills indicated that was not a working solution so the next year was with two cascading compressors. The third compressor was on sale at 25% off and was meant to be a spare for a when one died and like all of us, compressors will eventually die. Problem was my feeble mind kept wondering how it would run with three cascading compressors. It made a huge difference.

I am retired so the speed is not a problem, the first year I spent hovering and worrying over it with a laser thermometer, but these days with the third compressor I just set it, turn it on and then hike the high desert trails around the house while it fills my tank.9

I have $1200.and change in the CAT compressors and if memory serves me correctly, a rare occurrence these days, the Altaros was in the 700 dollar range.

Shipping is the biggest problem for me, neither the wife or I drive now so we need things delivered and picked-up, the CATs are easy to handle and the design with the built in roll bar helps protect it from damage by uncaring delivery folks. The shippers hve damaged 1 of 4 compressors and one of two storage tanks. The CAT compressor factory is one state away.

The DIY factor or what I call my “mad Scientist”phase which had me dream this up and assemble it was rewarding.

Make no mistake It, is just another PCP money pit that is hopefully now completed, but it is mine, I dreamed it up and assembled it. I enjoy it as much as the rifles it powers.

Roachcreek